This invention relates to an electronically controlled fluid suspension system comprising reserve tanks for controlling the vehicle attitude by fluid springs of the suspension.
There have been proposed a variety of the electronically controlled suspension systems which control the damping force of a shock absorber or the spring constant of an air spring in order to enhance riding comfort and steering stability. For example, in a system disclosed in Japan published unexamined utility model application No. 60-119608, the damping force of the shock absorber and the spring constant of the air springs at the left and right wheels are controlled upon detection of a predetermined lateral acceleration so as to prevent rolling, thus keeping the vehicle body horizontal. Another suspension system disclosed in Japan published unexamined utility model application NO. 60-119614 controls the damping force of the shock absorbers and the spring constant of the air springs at the front and rear wheels in response to detection of a predetermined front-to-rear acceleration or a predetermined pedal operating speed, so as to prevent the vehicle body from diving or squatting, thus keeping the vehicle body horizontal.
However, these electronically controlled suspension systems have some problems. More particularly, the prior art suspension systems alter the damping force of the shock absorbers to a higher degree and controls the spring constant of the air springs before the vehicle attitude starts changing, e.g., rolling, diving, or squatting. This alteration of the damping force to the higher degree may delay the time for the change of the vehicle height through the supply and discharge of the air to and from the air springs. Moreover, the predetermined alteration of the damping force prior to the vehicle's attitude change may deteriorate the riding comfort.